The present invention relates to a method of and apparatus for detecting diamonds in a rock sample, and can be used when prospecting for diamonds to locate microdiamonds in particulate mineral material.
When prospecting for diamonds, samples of rock, e.g. drill cores, are taken and are reduced to powder particles (particle size generally in the range from 50 to 300 micrometers ), e.g. by chemical treatment and grinding. This mineral powder is analyzed by taking samples and spreading the samples on microscope slides, which are then observed under a microscope by a skilled operator.
The rock samples may contain diamonds, usually in a very low concentration, and these will give rise to small diamonds or fragments of diamond--microdiamonds--in the powdered mineral sample. Thus diamondiferous rock may be identifiable by the presence of microdiamonds in the mineral powder samples.
Detecting microdiamonds in mineral powder samples is a very skilled job and very time consuming. The microdiamonds themselves may be graphite covered and very difficult to recognize. In most cases, there will be no microdiamonds in a sample, and a very large number of samples has to be processed as part of the prospecting process.
It is an object of the present invention to provide a method of and apparatus for detecting diamonds in a rock sample whereby diamond can be identified uniquely. It is also an object of the present invention to provide a method of and apparatus for detecting diamonds in a rock sample which can be carried out automatically by a machine.